The existence of the program and its widespread use was disclosed by former NSA contractor-turned-accuser Edward Snowden and documents allegedly proving its existence were shown to the newspaper.

In Washington, NSA spokesperson Judith Emmel said, "Any allegation that NSA relies on its foreign partners to circumvent U.S. law is absolutely false. NSA does not ask its foreign partners to undertake any intelligence activity that the U.S. government would be legally prohibited from undertaking itself.”

Snowden's disclosures over the past few weeks have ignited a political storm over the balance between privacy rights and national security. The NSA has defended the programs, saying they have disrupted possible attacks in the U.S.

The newspaper said on its website that Snowden had shown it documents about a project named “Tempora,” which had been running for more than a year and allowed GCHQ to tap into and store huge volumes of data drawn from cables for up to 30 days.

The U.S. government has filed criminal charges against Snowden, who fled to Hong Kong following The Guardian’s initial story uncovering the NSA surveillance programs. He reportedly wants to seek sanctuary in Iceland.

A WikiLeaks-linked Icelandic businessman claims to have prepped a private jet to fly Snowden to Iceland if the country approves his request for asylum.

"A private jet is in place in China and we could fly Snowden over tomorrow if we get positive reaction from the Interior Ministry. We need to get confirmation of asylum and that he will not be extradited to the US. We would most want him to get a citizenship as well," Reuters quoted Olafur Vignir Sigurvinsson as saying.